ZD, that is used to show his brilliance. Notice how in that story (which copies are available of his drawing, btw) the Chazon Ish didn’t do the surgery, and nor did the person come to him instead of a doctor.
Your reference to a referal is probably basedd on experience. Not everyone that is famous is the best. And, very often, people go to the top notch doctor for a minor procedure and it is a waste of money.
In either case, the person didn’t go to a Gadol for a prescription rather than to a doctor. Are you trying to refute one point with an unrelated one?